Posttranslational modification of the RHO of plants protein RACB by phosphorylation and cross-kingdom conserved ubiquitination

Small RHO-type G-proteins act as signaling hubs and master regulators of polarity in eukaryotic cells. Their activity is tightly controlled, as defective RHO signaling leads to aberrant growth and developmental defects. Two major pathways regulate G-protein activity: canonical switching of the nucleotide bound state and posttranslational modification (PTM). PTMs can support or suppress RHO signaling, depending on each individual case. In plants, regulation of Rho of plants (ROPs) has been shown to act through nucleotide exchange and hydrolysis, as well as through lipid modification, but there is little data available on phosphorylation or ubiquitination of ROPs. Hence, we applied proteomic analyses to identify PTMs of the barley ROP RACB. Data show in vitro phosphorylation by barley ROP Binding Kinase 1 and in vivo ubiquitination of RACB.